Isoflurane has been in use since the 1970s and more commonly in use in the veterinary setting since the late 1990s. As an anaesthetic agent, not surprisingly, it is capable of causing drowsiness or unconsciousness if large amounts are present in the room air. It has other known health effects including respiratory tract and skin irritation, as well as impacts on heart rate (increases) and blood pressure (decreases).
Epidemiological studies undertaken in the 1980s and 1990s showed reproductive concerns to workers exposed to isoflurane, including an increased risk of birth defects and miscarriage. However, it is important to note that this was prior to the widespread use of scavenging devices to remove the waste anaesthetic gas from the anaesthetic circuit, rather than release it into the room air.
In more recent times, various studies have been undertaken to monitor the health impacts on female veterinary workers exposed to isoflurane, with evidence indicating that when a scavenge is in use, the risk is low (pmc.ncbi.nlm.nih.gov/articles/PMC10048231/#:~:text=Results%3A%20The%20percentage%20of%20congenital,veterinarians%2C%20it%20was%207.1%25.)
Like any chemical, we should always ensure that our exposure to isoflurane is As Low As Reasonable Achievable (the ALARA principle). A recent study we undertook, demonstrated practically how to best do this (A study of worker isoflurane exposure levels in Australian veterinary workplaces, available at pubmed.ncbi.nlm.nih.gov/39951345.)
Summary of the study:
- Veterinary workers undertaking isoflurane anaesthetics in 2 busy small animal and one busy specialist equine clinic wore isoflurane monitoring badges during their work shift
- The isoflurane monitoring badges capture the same amount of isoflurane that the worker will be breathing in, allowing for this to be measured
- At each of these clinics they undertook specific isoflurane hazard controls to minimise exposure (all of which are easily achievable in any clinic, see below)
- In Australia, there is no Occupational Exposure Standard (OES) for isoflurane. An OES is a documented level above which workers are not permitted to be exposed to. In other parts of the world, various OES exist which range from 2- 50 ppm during an 8-hour work shift
- This study showed that all exposures were lower than the lowest international OES, confirming that exposures are low when good hazard controls are in place. PHEW!
And so, from a practical perspective, what did these clinics do to reduce exposure and therefore what should we all be doing?
- ACTIVE scavenging (with a pump/vacuum device), which are far superior to passive scavenging (charcoal cannisters or similar) in preventing work room isoflurane levels to increase
- Leak testing of circuitry prior to each use
- Using a cuffed ET tube for each anaesthetic
- Having room ventilation in the form of a door open (where permitted), or air conditioning or an extraction fan on
- Refilling vaporisers the least number of times per day, and when the least number of staff are present (e.g. the very start and end of the day)
- Minimising box and mask inductions (which leak a large amount of isoflurane in the work room)
- Allowing the patient to breath pure oxygen via the circuitry until extubation (to allow the scavenge system to remove breathed-off isoflurane, rather than having it entering the room air).
Have a chat to your team at your next staff meeting about these steps and implement them to ensure your team members’ exposures are kept very low also!
